Diesel's massive 30th-anniversary bash last October included trapeze artists, fire eaters, a roller derby, and a heady roster of musical heavyweights such as M.I.A., Franz Ferdinand, T.I., N.E.R.D., and Chaka Khan, among others. So when I received an invite to last night's Diesel:U:Music show at Webster Hall, with mention of a special guest collaboration, I was anxious to find out what surprises the denim megabrand had in store. Though the concert—whose lineup listed headliners the Roots, Passion Pit (whose recent electropop outing Manners is the perfect summer soundtrack), Cobra Starship (who sang "Good Girls Go Bad" sans Leighton Meester), and Brooklyn MC Theophilus London—didn't reach the epic proportions of last year's blowout, it was impressive nonetheless, featuring unexpected appearances by the Clipse, assisted by Kanye West for "Kinda Like a Big Deal," and Swedish songstress Lykke Li, who joined the Roots on stage for the final act. We stole a few minutes backstage with Li (pictured) before her big performance.

—Erin Clements

How did tonight's collaboration with the Roots come about?

Their management and Diesel approached me and asked. And of course you want to play with the Roots! I'm a very big fan.